Hi hgilmer,
Your PC will run BOBII well in most missions. Some of the Missions with 200-300 a/c in the air may bog it down some (but that happens with my PC also). You may need to cut setting a bit to keep you FPS in the higher range. Again see the performance thread for the key settings to keep your FPS higher.
http://a2asimulations.com/forum/viewtopic.php?t=10091
You also may want to come to the forum and read it some.
http://shockwaveproductions.com/forum/index.php
We are getting ready to deliver our 2.08 update for all the customers which will install over your purchase (if you decide to buy).
As a comparison here are my PC spec: Intel Core2 Extreme processor QX6700(2.66GHz,1066FSB) 8MB cache, 2GB DDR2 SDRAM @667MHz, 768MB NVIDIA GeForce 8800 GTX, Sound Blaster X-Fi PCI Sound Card, Direct X 9.0C, XP SP2 , CH Fighter Stick & Pedals ,TrackIR4 Pro thanks to BobII crew.